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Trigger for 2010 An operation point of view

Trigger for 2010 An operation point of view. Constraints What we learned from 2009 Overall issues Proposal . What we learned from 2009. Working at low threshold is unstable HCAL at 240 MeV threshold can count a lot Several 100,000 when one channel was ‘hot’

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Trigger for 2010 An operation point of view

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  1. Trigger for 2010An operation point of view Constraints What we learned from 2009 Overall issues Proposal

  2. What we learned from 2009 Trigger 2010 from operation • Working at low threshold is unstable • HCAL at 240 MeV threshold can count a lot • Several 100,000 when one channel was ‘hot’ • Hot channels (i.e. Large fluctuating pedestal) are not understood • Masking them was the only solution. • A coincidence is needed at low threshold • If one trigger channel has 1% noise, it counts 400 kHz. • But with a coincidence to something else this is almost innocuous. • L0 should be coincidences at low threshold • HCAL(+ECAL) and SPD • 5 Muon stations

  3. Do we need a PUS trigger? Trigger 2010 from operation • Due to noise, PUS has to have a high threshold • Was set to 7 in 2009 • Some very bizarre events with high digital multiplicity but nothing on the analogue readout, so called OT monitoring problem. • What is the role of PUS trigger? • Beam2-gas is handled differently • New Beam-Gas trigger (L0 independent decision) in coincidence with empty-beam crossings • This gives a factor ~1000 extra rejection at start, less when more bunches, but > 100. • We can have a reasonably low threshold in beam-gas mode • Any reason to trigger physics events with PUS? • I don’t see one.

  4. Global constraints Trigger 2010 from operation • 1 MHz at L0 • Not an issue for the first few months, if we have a robust L0 not sensitive to noise / pick-up. • In fact less due to several problems with FE electronics • << 16 event de-randomiser -> dead time comes soon into the game. • Processing speed in HLT • Nominally 300 kHz with the full HLT farm • Output rate • 2 kHz on storage • Physics rate after stripping < 100 Hz • Keep the data at a manageable size.

  5. Proposal for L0 Trigger 2010 from operation • Minimum bias trigger • CALO: Similar to 2009, i.e. low threshold + SPD > 2 • Add ECAL to HCAL to have a better threshold/efficiency • Noise rate to be re-assesed to define the threshold, but 240 MeV is a good guess. • Muon: low Pt. In fact the cut is in momentum to reach M5, and in sizes of FOI to cope for multiple scattering. • However FOM are the same for Minimum bias and physics trigger... • No PUS trigger. • Luminosity trigger • Random according to bunch pattern • Reasonable rate, agreed to be less than 100 Hz by the lumi responsible and the management • Ration 1024 : 32 : 8 : 8 means 64 : 1 : 0.25 : 0.25 Hz for example. • Need for higher rate needs to be justified.

  6. Trigger 2010 from operation • Normal physics L0 • from Hans’s presentation on 20 November 09 • Hadron > 2000 MeV • Electron > 1440 MeV • Photon > 2980 MeV • Muon > 1040 MeV • Pi0 ?? • No global event cuts. • No easy identification of these events compared to Minimum Bias • Same event type • Has to dig into the L0DU bank..

  7. Trigger 2010 from operation • Beam-gas trigger • Uses the beam pattern, triggers only on b+e and e+b. • Beam1-Empty: SumEt high, PUMult low • Empty-Beam2: PUMult high, SumEt low • What are reasonable values? • This trigger is to measure the beam transverse profile • The only output is the sigma of the distribution • In fact an extrapolation of the beam envelope, somewhat conic. • Error on sigma is sigma/sqrt( 2*N) • For 1% relative error, one need 5,000 events... • One need this number every ~10 minutes • 100 Hz would give 60,000 triggers per 10 minutes • Change of the thresholds and/or downscale factors implies a new TCK to be released. • Not easy in fact... • Better have a safe conservative value!

  8. HLT output rate Trigger 2010 from operation • As always stated, 2 kHz is a maximum • Buffer exist to absorb spikes of a few seconds, not minutes... • Express stream and Lumi stream • These loads also the storage • Express stream ~ 5 Hz nominal • This has to be implemented intelligently, as now we just have a downscaler... • Lumi stream < 100 Hz • 1 kHz of physics events -> 3.6 million an hour • Storage and processing later become critical • Stripping needed to keep the useful rate to < 100 Hz

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